This is the 92nd most frequent Hebrew word.
מהם
"מהם" means "from them" or "of them" in English.
In this question, 'מהם' functions as a pronoun meaning 'what are'. It's used to ask about the definition or identity of the subject, in this case, 'habits'.
מהם ההרגלים החשובים ביותר לחיים בריאים?
What are the most important habits for a healthy life?
In this instance, 'מהם' again means 'what are' and is used to ask for a description or list of the main elements of the dish.
מהם המרכיבים העיקריים של תבשיל זה?
What are the main ingredients of this dish?
Here, 'מהם' means 'of them' and serves to refer to one item from a previously mentioned plural group.